Large scale magnetic field of the Milky Way from WMAP3 data

TL;DR

This paper analyzes WMAP3 polarization data to model the Milky Way's large-scale magnetic field, highlighting current limitations and proposing future UHECR data to resolve model ambiguities.

Contribution

It demonstrates how polarization data constrains magnetic field models and discusses the potential of ultra-high-energy cosmic ray data to improve model discrimination.

Findings

Polarization data constrains some model parameters.

Data cannot uniquely determine the magnetic field model.

Future UHECR data can help distinguish model symmetries.

Abstract

We report on initial results from a project to constrain the large-scale and turbulent magnetic fields of the Milky Way galaxy, which eventually will incorporate all of the relevant observational data. In this paper we fit popular large scale magnetic field models to WMAP3 polarization maps. We find that the polarization data can constrain certain model parameters but does not uniquely determine the best-fit parameters. We also find that the polarization data alone cannot distinguish between model symmetries, e.g., the existence of field reversals. We show how future UHECR data can break this degeneracy.